Exophoria is a form of heterophoria in which there is a tendency for the eyes to deviate outward. [1] During inspection, when the eyes dissociate like a prism, the visual axes will diverge from each other. [2]
| Exophoria | |
|---|---|
| ICD-10 | H 50.5 |
| ICD-9 | 378.42 |
Prevalence
Exophoria is especially common in infancy and childhood , and increases with age. [3]
Reasons
Exophoria can be caused by several factors, which include:
- Anomalies of refraction - deviations to the far and near distance are approximately equal.
- Excessive divergence - exo-deduction of more than 15 diopters more at a long distance than at close.
- The lack of convergence - exo-deviation at a short distance is greater than at a far distance.
Exophoria may be due to nervous, muscle, or congenital problems, or due to mechanical abnormalities. Unlike divergent strabismus , fusion is possible in this state, as a result of which diplopia is rare.
Notes
- ↑ Allen, Edmund Turney. The science of higher prisms . - Harvard University: GK Hazlitt 6 Co., printer, 1899.
- ↑ Grosvenor, Theodore. Primary Care Optometry 5th Ed. - Butterworth-Heinemann, 2007 .-- ISBN 978-0-7506-7575-8 .
- ↑ Freier B E., Pickwell L D. Physiological exophoria (neopr.) // Ophthalmic and Physiological Optics. - 1983 .-- T. 3 . - S. 267—272 . - DOI : 10.1111 / j.1475-1313.1983.tb00613.x .